The verdict is in: Preserving bat habitats makes sense in curbing Hendra virus risk

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A coloured transmission electron micrograph of the Hendra, virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency CC BY 3.0 via Wikimedia Commons
A coloured transmission electron micrograph of the Hendra, virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency CC BY 3.0 via Wikimedia Commons

Ecological strategies should be part of the approach to reduce the risk of Hendra virus spillovers in Australia, according to members of the public who sat on “community juries” to hear evidence.

Three community juries were unanimous in their view, according to a study published in the open-access peer-reviewed journal PLOS ONE.

Hendra is a virus carried by Australian fruit bats, known as flying foxes. The virus is able to infect horses. Contact with the infected bodily fluids of horses can cause infections in humans, with four of the seven known cases resulting in death.

Habitat loss has increased the presence of flying foxes in built-up areas, increasing the risk of contact and therefore viral “spillovers” into horse and human populations.

A horse vaccine is available and horse-husbandry practices that minimize exposure to the virus are encouraged, but their adoption is considered sub-optimal.

The idea that ecological approaches, such as habitat creation and conservation, could complement vaccination and behavioural strategies, has been proposed. However, such measures could be considered highly controversial if they are perceived as placing limits on economic development and restricting the rights of landholders.

Researchers are nevertheless beginning to explore the possibility of creating and conserving flying fox habitat as a public health intervention against current and future disease risks

University of Wollongong researcher Chris Degeling and his colleagues convened three community juries to elicit the views of citizens on the acceptability of adding ecological approaches to current Hendra strategies.

They study team said that while such juries cannot possibly represent a statistically characterized sample of the general public, it was possible to derive a sense of what an informed public would advise from their conclusions after deliberating on the evidence.

One of the juries was in Rockhampton (Central Queensland), one in Lismore (Northern New South Wales) and one further south in Sydney.

The juries collectively comprised 31 randomly selected participants of diverse backgrounds, mixed genders and ages. They comprised a mix of horse owners and those who did not own horses.

Each jury was presented with balanced, factual evidence. Members were given time to ask questions of expert presenters and, after deliberations, come to conclusions based on the evidence.

“All juries voted unanimously that ecological strategies should be included in Hendra virus risk management strategies,” the study team reported, “but concluded that current interventions – including vaccination and changing horse-husbandry practices – must remain the priority.”

The key reasons given for adopting ecological approaches were:

  • They address underlying drivers of disease emergence;
  • The potential to prevent spillover of other bat-borne pathogens; and
  • There would be broader community benefits.

Juries differed on the best mechanism to create/conserve flying fox habitat. Participants in regional centres favoured direct government action, whereas the metropolitan jury preferred to place the burden on landholders.

The researchers concluded that citizens, when given balanced evidence, acknowledged the value of addressing the drivers of bat-borne infectious risks but differed on the best way to implement them.

“Ecological approaches to securing bat habitat could find broad social support in Australia, but disagreement about how best to achieve them indicates the need for negotiation with affected communities to co-develop fair, effective and locally appropriate policies,” they said.

“The unanimous verdicts of our community juries suggest that ecological approaches to Hendra virus risks are likely to be acceptable to citizens if they are informed about the costs, benefits and limitations of different types of intervention.

“Yet the acceptance of, and adherence by the population to, public health measures directed against infectious disease risks depend largely on the way people perceive the threat.

“When the juries’ verdicts are compared, those in Rockhampton and Lismore (which had been previously impacted by HeV spillovers) prioritised the need for reliable and rapidly effective prevention.

“Risk perceptions and previous personal experience are central to people’s decisions about how they protect themselves from infectious disease risks.”

None of the jurors in Rockhampton or Lismore proved indifferent to the ecological drivers of spillovers.

“However, the responses of both juries in these areas – where public health benefit from ecological approaches would be greatest – was clear. Ecological approaches to mitigate spillovers would be a luxury unless resources were also made available to mitigate proximal risks, such as by providing subsidised equine vaccination.

“Safeguarding human health must take priority over measures aimed at improving the health of flying fox populations.”

The researchers noted that successful implementation of ecological approaches to Hendra would depend on navigating longstanding tensions in Australia about how best to manage and distribute the benefits and burdens of land use between privately owned primary industries and taxpayers.

“In Rockhampton, an area where regulatory restrictions on land clearing have historically had significant electoral implications, the jury wanted the costs and burdens of any ecological approaches to be borne by government, because the outcome would be for broader public benefit.

“On the other hand, in metropolitan Sydney, the jury held that landholders should bear the cost of the upkeep of their assets and habitat protection and rehabilitation.

“The Lismore jury was divided on this question, eventually reaching a compromise that placed burdens on both landholders and governments.

“Communities in regional and rural northern Australia can be particularly sensitive to centralised decision-making which is sometimes viewed as an incursion on the rights and interests of local residents.

“People living on the land perceive that the academics and ‘city-dwellers’, proposing conservation measures, are ignorant of local conditions and the practical and moral implications of expecting landholders to solve environmental problems.”

The full study team comprised Chris Degeling, Gwendolyn L. Gilbert, Edward Annand, Melanie Taylor, Michael G. Walsh, Michael P. Ward, Andrew Wilson and Jane Johnson, from a range of tertiary institutions.

Degeling C, Gilbert GL, Annand E, Taylor M, Walsh MG, Ward MP, et al. (2018) Managing the risk of Hendra virus spillover in Australia using ecological approaches: A report on three community juries. PLoS ONE 13(12): e0209798. https://doi.org/10.1371/journal.pone.0209798

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